"According to our information, around 15 armed men who were wearing Pakistan army uniform stopped the buses," Umarzai said. "They disembarked all the passengers and checked their identity cards and then opened fire at them. But this is initial information and death toll could rise as the area is far away and it will take some time in reaching complete information to us."

He said a group of foreign visitors, including a party of Japanese travelers, informed them about the incident.

Police official Shah Nawaz said most of the people traveling in buses were from Shiite Muslim community. He said they were using the Kaghan-Naran route because of previous attacks on the Karakurram highway.

Air base attackEarlier, militants attacked a military air base in Pakistan, prompting a five-hour firefight that killed two security guards and six attackers and left the base commander seriously injured.

The militants, wearing military uniforms and suicide vests, entered the Kamra airbase, close to the capital, Islamabad.

A Pakistan Air Force spokesman said the militants attacked the air base where JF-17 Thunder planes are assembled. However, the spokesman said those aircraft were not present at the airbase during the attack.

Security officials inside the base said some security personnel have been injured in exchange of fire with the militants.

No militant group has so far claimed responsibility for the attack but Pakistani security officials believed the Tehrik-e-Taliban Pakistan or TTP headed by Hakimullah Mahsud could be behind the attack.

Pakistani intelligence agencies had released reports a few days ago and said that militants could attack PAF and other military installations during the final week of Ramadan, the Islamic holy month.